This study's primary objective is to evaluate the associations of in utero environmental exposures with newborn and infant health outcomes. The study will be conducted in two phases: (1) a baseline cross-sectional survey of the population at birth, and (2) a follow up analysis (longitudinal component) of the phase 1 study population during infancy to evaluate any delayed developmental effects of intrauterine toxin exposures. The specific exposures of interest occur through maternal-placental transfer and include; polychlorinated biphenyls (PCGs), pesticides (DDE), lead (Pb), cadmium (Cd), and mercury (Hg). We are evaluating the relationship between these exposures and a variety of developmental outcomes including measures of infant size (weight, head circumference, crown-heel length, skinfold thickness), infant behavior and neurologic function (the Brazelton Neonatal Behavioral Assessment Scale or NBAS, infant cry acoustics, the Fagan Test of Infant Intelligence, and the Bayley Scales of Infant Development-II). The study is designed to perform two baseline evaluations (at birth ad at one week of age) and one follow up evaluation (at 607 months of age) on a subsample of 475 mother-infant pairs who deliver at St. Luke's Hospital in new Bedford, Massachusetts and who live in one of four communities adjacent to the New Bedford Harbor Superfund site. Important contaminants at this Superfund site include PCBs, lead, and cadmium. One of the primary risk factors for potential exposures to these toxins among this population is residence in the New Bedford area. In addition, new Bedford's aging housing increases the risk of environmental lead exposure in this population. Lastly, results of preliminary studies indicate that mothers in this population consume moderate amounts of fish (average 0.7 servings/day) and 17% consume locally caught fish, risk factors for both PCB an mercury exposures. There is emerging evidence of associations between low level in utero exposures to each of PCBs, DDE, lead, cadmium, and mercury and changes in developmental achievement and growth in infancy and/or later childhood. Corroborating results of previous research in this area and achieving a better understanding of the developmental consequences of in utero exposures to these persistent environmental contaminants and known neurologic toxins is of great public health importance. This understanding is necessary for identifying critical periods for intervention and exposure and disease prevention.